Heat dissipation device and airflow generator thereof

ABSTRACT

An exemplary heat dissipation device includes a heat sink defining a plurality of air passages therein, and an airflow generator disposed at a side of the heat sink. The airflow generator includes airflow-generating units stacked together. Each airflow-generating unit includes a casing in which two spaced vibration diaphragms are received, and a nozzle connected to the casing. A chamber is defined between the two vibration diaphragms within the casing. The nozzle defines an air channel therein for communicating the chamber with an exterior of the casing. Two piezoelectric elements are respectively attached to the two vibration diaphragms. When the two piezoelectric elements drive the two vibration diaphragms towards each other, the two vibration diaphragms compress the air in the chamber and drive the air towards the air channel of the nozzle, thereby generating an airflow from the nozzle towards the air passages of the heat sink.

BACKGROUND

1. Technical Field

The disclosure generally relates to heat dissipation; and moreparticularly to a heat dissipation device incorporating an airflowgenerator.

2. Description of Related Art

With developments in electronic components such as central processingunits (CPUs), such components are nowadays capable of operating at veryhigh speeds. The amount of heat generated by such components duringnormal operation is commensurately large. If not quickly removed from aCPU, this generated heat may cause the CPU to become overheated andfinally affect its workability and stability.

In order to remove the heat from a CPU and hence enable normaloperation, a heat dissipation device is usually provided. A frequentlyused heat dissipation device includes a fan with a heat sink arranged atan outlet thereof, with the heat sink thermally connected to the CPU viaa heat pipe. Heat generated by the CPU is transferred to fins on theheat sink via the heat pipe. Airflow from the fan crosses the fins ofthe heat sink and removes the heat from the fins to the exterior of thesystem.

However, when running at high speeds, the fan generates noise. Inaddition, an impeller of the fan usually increases the size of the heatdissipation device, compromising efforts to limit the size of thecorresponding electronic product.

What is needed, therefore, is a means to overcome the describedlimitations.

BRIEF DESCRIPTION OF THE DRAWINGS

Many aspects of the present embodiments can be better understood withreference to the following drawings. The components in the drawings arenot necessarily drawn to scale, the emphasis instead placed upon clearlyillustrating the principles of the present embodiments. Moreover, in thedrawings, like reference numerals designate corresponding partsthroughout the several views.

FIG. 1 is an isometric, assembled view of a heat dissipation device inaccordance with an exemplary embodiment of the present disclosure.

FIG. 2 is an exploded view of the heat dissipation device of FIG. 1.

FIG. 3 is similar to FIG. 2, but viewed from a different aspect.

FIG. 4 is a cross-section of the heat dissipation device of FIG. 1,taken along a line IV-IV thereof.

FIG. 5 is a schematic view corresponding to FIG. 4, showing a firststage of operation of one airflow-generating unit of the heatdissipation device of FIG. 1.

FIG. 6 is similar to FIG. 5, but showing a second stage of operation ofthe airflow-generating unit of the heat dissipation device of FIG. 1.

FIG. 7 is similar to FIG. 6, but showing a third stage of operation ofthe airflow-generating unit of the heat dissipation device of FIG. 1.

DETAILED DESCRIPTION

Referring to FIGS. 1-3, a heat dissipation device 100 according to anexemplary embodiment of the present disclosure is shown. The heatdissipation device 100 includes an airflow generator 10 and a heat sink20. In a typical application, a heat-generating electronic component(not shown) generates heat, and such heat is transferred from theheat-generating electronic component to the heat sink 20.

Referring also to FIG. 4, the airflow generator 10 includes a shell 11and a plurality of airflow-generating units 12. The airflow-generatingunits 12 are arranged in the shell 11, and are stacked togetherhorizontally. Each airflow-generating unit 12 includes a casing 121, twovibration diaphragms 122 received in the casing 121, and a nozzle 123arranged at an end of the casing 121.

The casing 121 is cuboid. The two vibration diaphragms 122 arehorizontally mounted in the casing 121 at different levels. The twovibration diaphragms 122 are spaced from and parallel to each other. Aninner space of the casing 121 is divided by the two vibration diaphragms122 into a first chamber 124 between the two vibration diaphragms 122, asecond chamber 125 located above the first chamber 124 and isolated fromthe first chamber 124 via a top one of the vibration diaphragms 122, anda third chamber 126 located below the first chamber 124 and isolatedfrom the first chamber 124 via a bottom one of the vibration diaphragms122. Each vibration diaphragm 122 is elastic material, such as rubber,flexible resin or a thin metal sheet.

Two piezoelectric elements 127 are received in the second chamber 125and the third chamber 126 of the casing 121, respectively. The twopiezoelectric elements 127 are respectively attached to middle portionsof the two vibration diaphragms 122, so as to vibrate substantiallyperpendicularly to the two vibration diaphragms 122 when an alternatingvoltage is applied to the piezoelectric elements 127. Each piezoelectricelement 127 is made of piezoelectric ceramic. Through holes (notlabeled) are defined in a sidewall of the casing 121 for extension ofwires 128 therethrough to electrically connect the piezoelectricelements 127 on the two vibration diaphragms 122 with an external powersupply (not shown).

The nozzle 123 is disposed at the end of the casing 121 which faces theheat sink 20. The nozzle 123 is connected to a middle portion of thesidewall of the casing 121 at the end of the casing 121, and correspondsto the first chamber 124. The nozzle 123 defines a tapered air channel1231 therein. A large end of the air channel 1231 communicates with thefirst chamber 124, and a small end of the air channel 1231 is adjacentto the heat sink 20.

The shell 11 defines a receiving space (not labeled) therein, with anopening 111 of the receiving space adjacent to the heat sink 20. Thestacked airflow-generating units 12 are arranged into the shell 11 viathe opening 111. The shell 11 fixes the stacked airflow-generating units12 together. In other embodiments, the stacked airflow-generating units12 can be fixed together by adhesive or glue.

The heat sink 20 includes a plurality of spaced fins 21, with aplurality of air passages 22 defined between the fins 21. The airflowgenerator 10 is arranged at a lateral side of the heat sink 20, with thenozzles 123 of the airflow-generating units 12 facing the air passages22 of the heat sink 20. The small end of the nozzle 123 of eachairflow-generating unit 12 is spaced a predetermined distance from anentrance of a corresponding air passage 22 of the heat sink 20.

In operation, the external power supply provides an alternating voltageto the two piezoelectric elements 127 of each airflow-generating unit 12via the wires 128. As a result of the reverse piezoelectric effect, thetwo piezoelectric elements 127 produce alternating expansion andretraction, driving the two vibration diaphragms 122 up and down. Inparticular, the two vibration diaphragms 122 bend towards each othersimultaneously or bend away from each other simultaneously. When the twopiezoelectric elements 127 drive the two vibration diaphragms 122towards each other, the two vibration diaphragms 122 compress the air inthe first chamber 124 towards the air channel 1231 of the nozzle 123,generating airflow towards the air passages 22 of the heat sink 20 fromthe small end of the nozzle 123. The airflow along the air passages 22of the heat sink 20 removes heat present in the fins 21.

Referring to FIGS. 5-7, an airflow-generating process of eachairflow-generating unit 12 in one vibrating period is as follows:

The airflow-generating process is divided into a first stage, a secondstage, and a third stage. In the first stage, the external power supplyprovides a negative/positive voltage to the two piezoelectric elements127 via the wires 128, and the two piezoelectric elements 127 drive thetwo vibration diaphragms 122 towards each other. The air in the firstchamber 124 is compressed by the two vibration diaphragms 122 and flowstowards the air channel 1231 of the nozzle 123. Referring to FIG. 5,when the two vibration diaphragms 122 move from originally horizontalpositions to curved positions indicated by broken lines 122 a, a firstairflow 31 is generated towards the air passages 22 of the heat sink 20from the outer end of the nozzle 123. The first airflow 31 along the airpassages 22 of the heat sink 20 results in heat exchange from the fins21 to the air, and the heat of the fins 21 is thereby removed.

In the second stage of the airflow-generating process, thenegative/positive voltage supplied to the two piezoelectric elements 127is inverted to a positive/negative voltage, such that the twopiezoelectric elements 127 drive the two vibration diaphragms 122 awayfrom each other. Referring to FIG. 6, when the two vibration diaphragms122 return from the curved positions indicated by broken lines 122 b(see in FIG. 5) back to the horizontal positions, the air outside andaround the nozzle 123 is drawn into the air passages 22 of the heat sink20, generating a second airflow 32 along the air passages 22 of the heatsink 20, at a flow rate about ten times that of the first airflow 31.

In the third stage of the airflow-generating process, the two vibrationdiaphragms 122, as shown in FIG. 7, continue to move farther way fromeach other until they reach the curved positions indicated by brokenlines 122 b. During this stage, the volume of the first chamber 124 isexpanded, such that cool air (indicated by arrows 33) outside and aroundthe nozzle 123 is drawn into the first chamber 124 of the casing 121.Then the positive/negative voltage supplied to the two piezoelectricelements 127 is inverted to the negative/positive voltage, and the firststage of the airflow-generating process begins again.

In each airflow-generating unit 12, under the alternating voltage, thetwo piezoelectric elements 127 drive the two vibration diaphragms 122 toperiodically compress the air in the first chamber 124 of the casing121, generating airflow towards the air passages 22 of the heat sink 20from the outer end of the nozzle 123. In addition, by supplyingalternating voltages of different frequencies, the flow rate of theairflow generated by the airflow-generating unit 12 can be adjusted tomeet different cooling requirements.

In the heat dissipation device 100, the heat transferred to the fins 21of the heat sink 20 is dissipated from the fins 21 by the airflowgenerator 10. The number of airflow-generating units 12 of the airflowgenerator 10 can be chosen to meet the cooling requirements of aparticular application. Further, no motor or impeller is used in theheat dissipation device 100. Thus the heat dissipation device 100 canhave a small size and quiet operation.

It is to be understood, however, that even though numerouscharacteristics and advantages of the present embodiments have been setforth in the foregoing description, together with details of thestructures and functions of the embodiments, the disclosure isillustrative only, and changes may be made in detail, especially inmatters of shape, size, and arrangement of parts within the principlesof the disclosure to the full extent indicated by the broad generalmeaning of the terms in which the appended claims are expressed.

1. An airflow generator, comprising: at least one airflow-generatingunit, comprising: a casing; two spaced vibration diaphragms received inthe casing, with a chamber defined between the two vibration diaphragms;a nozzle connected to a sidewall of the casing in a positioncorresponding to the chamber, an air channel defined in the nozzle andcommunicating the chamber with an exterior of the casing; and twopiezoelectric elements respectively attached to the two vibrationdiaphragms, the two piezoelectric elements capable of vibratingsubstantially perpendicularly to the two vibration diaphragms whenvoltage is applied to the two piezoelectric elements and thereby drivingthe two vibration diaphragms to vibrate, whereby when the twopiezoelectric elements drive the two vibration diaphragms towards eachother, the two vibration diaphragms compress the air in the chamber ofthe casing and drive the air towards the air channel of the nozzle,generating an airflow from the nozzle to the exterior of the casing. 2.The airflow generator of claim 1, wherein the air channel of the nozzleis tapered from an inner end of the nozzle adjacent to the chambertowards an opposite outer end of the nozzle.
 3. The airflow generator ofclaim 1, wherein the two vibration diaphragms are parallel to eachother.
 4. The airflow generator of claim 1, wherein the casing iscuboid.
 5. The airflow generator of claim 1, wherein the piezoelectricelements are attached to middle portions of the two vibrationdiaphragms, respectively.
 6. The airflow generator of claim 1, furthercomprising a shell in which the at least one airflow-generating unit ismounted.
 7. A heat dissipation device, comprising: a heat sink defininga plurality of air passages therein; and an airflow generator disposedat a side of the heat sink, the airflow generator comprising: aplurality of airflow-generating units stacked together, each of theairflow-generating units comprising: a casing; two spaced vibrationdiaphragms received in the casing, between which a chamber is defined; anozzle disposed at a lateral side of the casing facing the heat sink andconnected to a sidewall of the casing, an air channel defined in thenozzle and communicating the chamber with an exterior of the casing; andtwo piezoelectric elements respectively attached to the two vibrationdiaphragms, the two piezoelectric elements capable of vibratingsubstantially perpendicularly to the two vibration diaphragms whenvoltage is applied to the two piezoelectric elements and thereby drivingthe two vibration diaphragms to vibrate, whereby when the twopiezoelectric elements drive the two vibration diaphragms towards eachother, the two vibration diaphragms compress the air in the chamber ofthe casing and drive the air towards the air channel of the nozzle,generating an airflow from the nozzle to at least one of the airpassages of the heat sink.
 8. The heat dissipation device of claim 7,wherein the air channel of the nozzle is tapered from an inner end ofthe nozzle adjacent to the chamber towards an opposite outer end of thenozzle.
 9. The heat dissipation device of claim 7, wherein the twovibration diaphragms are parallel to each other.
 10. The heatdissipation device of claim 7, wherein the casing is cuboid.
 11. Theheat dissipation device of claim 7, wherein the piezoelectric elementsare attached to middle portions of the two vibration diaphragms,respectively.
 12. The heat dissipation device of claim 7, wherein theairflow generator further comprises a shell in which theairflow-generating units are mounted.
 13. The heat dissipation device ofclaim 7, wherein the heat sink comprises a plurality of stacked fins,the air passages are defined between adjacent fins, and the air passagesare aligned with the airflow-generating units.
 14. A heat dissipationdevice, comprising: a heat sink defining a plurality of air passagestherein; and an airflow generator disposed at a side of the heat sink,the airflow generator comprising a plurality of airflow-generating unitsstacked together, each airflow-generating unit comprising: a casing; twovibration diaphragms received in the casing, the diaphragms defining achamber therebetween; a nozzle extending from a sidewall of the casingat a position corresponding to the chamber, the nozzle defining an airchannel therein, the air channel communicating the chamber with anexterior of the casing; and two piezoelectric elements received in thecasing and attached to the diaphragms, respectively, the piezoelectricelements configured for driving the diaphragms to vibrate such that whenthe piezoelectric elements drive the diaphragms towards each othersimultaneously, the diaphragms compress the air in the chamber and drivethe air into the air channel of the nozzle, thereby generating anairflow from the nozzle to at least one of the air passages of the heatsink.
 15. The heat dissipation device of claim 14, wherein thepiezoelectric elements are further configured for driving the diaphragmsto vibrate such that when the piezoelectric elements drive thediaphragms away from each other simultaneously, air outside and aroundthe nozzle is drawn into the at least one air passage of the heat sink,generating an airflow along the at least one air passage.
 16. The heatdissipation device of claim 15, wherein the piezoelectric elements arefurther configured for driving the diaphragms to vibrate such that whenthe piezoelectric elements drive the diaphragms away from each othersimultaneously, the volume of the chamber is eventually expanded and airoutside and around the nozzle is drawn into the chamber.
 17. The heatdissipation device of claim 15, wherein when the diaphragms move towardseach other simultaneously and thereby generate an airflow from thenozzle to the at least one air passage of the heat sink, resultingairflow along the at least one air passage has a first flow rate; whenthe diaphragms move away from each other simultaneously and air outsideand around the nozzle is drawn into the at least one air passage of theheat sink and generates an airflow along the at least one air passage,such airflow has a second flow rate; and the second flow rate is greaterthan the first flow rate.
 18. The heat dissipation device of claim 17,wherein the second flow rate is about ten times the first flow rate.